Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 110310
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1010 PM EST Sat Dec 10 2016

.UPDATE...
The NEAR TERM Section has been updated below.

&&

.SYNOPSIS...
Issued at 307 PM EST Sat Dec 10 2016

A high Plains system will lift northeast across the great lakes
Sunday night. This system will bring snow to central Indiana
tonight. The snow will transition to a wintry mix and then rain
Sunday afternoon and evening as a warm front lifts northeast
across the area. Colder air will move in Monday in the wake of a
associated cold front.

Two more systems will bring much colder air in as well as chances
for accumulating snow Wednesday and Wednesday night and also next
weekend.

&&

.NEAR TERM /Overnight/...
Issued at 1010 PM EST Sat Dec 10 2016

Light but steady snowfall continues across the northern half of
the forecast area this evening as a warm front lifts north through
the region. Evaporative cooling processes have helped to pull
temps down as low as the mid 20s over far northern counties at
03Z...with upper 20s to near 30 further south.

The primary focus for the update is the snow which should continue
over the northern third of the forecast area for the next several
hours. Heaviest snow so far has been focused over far northern
sections of the forecast area. A mid level deformation axis and
isentropic lift contributing to the snowfall currently...but
expect that to shift northeast after 06Z with snow lightening up
and decreasing in coverage as it focuses over northern Indiana.
Will bump up to categorical pops for the next several hours over
far northern counties diminishing to no pops south of I-70.
Anticipate max amounts of 1-1.5 inches in a band from near
Lafayette E/SE through Kokomo to northern Madison County and the
Muncie area.

Expect temps to move little the rest of the night...likely holding
in the mid to upper 20s over much of the forecast area. Southeast
winds will be less than 10mph for the duration of the night.

Zone and grid updates out.

&&

.SHORT TERM /Sunday through Tuesday/...

Issued at 307 PM EST Sat Dec 10 2016

Snowfall amounts and timing of changeover will be the main
concern for the short term.

Models now in decent agreement that 295K isentropic lift will ramp
up as a low pressure system lifts northeast from the Plains to
Lake Huron Monday morning. This will result in increasing chances
of precipitation. Based on critical thickness progs, model
soundings and Bufkit, model blend has the far southwestern
counties dry until 15z Sunday at which time the precipitation type
should be either rain or freezing rain. The other areas should all
be snow. The freezing line will be working its way northeast and
should reach Greensburg, Indianapolis and Crawfordsville around 2
pm and extreme northern parts of the forecast area after 6 pm. Far
northern parts of Carroll county may remain snow the whole event
before it ends overnight Sunday night. Model QPF has increased a
bit and looks reasonable seeing as specific humidities reach 4 to
6 g/kg Sunday afternoon. In addition, the area will be in the
right rear quadrant of a 140 knot upper jet over southern lower
Michigan. Could see over 4 inches of storm total snow in the
advisory area with an inch or less from Indianapolis and south.
Could also see light freezing rain accumulation Sunday afternoon
with less than .05 expected. The remainder of the short should be
dry and cold with some breaks in the clouds.

&&

.LONG TERM /Tuesday night through Saturday/...

Issued at 229 PM EST Sat Dec 10 2016

A large upper low traversing northern Ontario will bring mostly
dry and colder weather to central Indiana to start the long term.
What once looked like potential for a strong storm mid week now
looks anemic in terms of forcing and moisture and thus only have a
slight chance for snow across the northern half or so of the area
during the day on Wednesday, and accumulations are very light.
Wind chills could drop below zero Wednesday night and Thursday
night.

By Friday though models indicate that an upper ridge axis could
move east of the state and allow a strong frontal system to form
in the southwestern states and quickly bring some moisture and
forcing back to the area on southwesterly flow. Thus have chances
for snow going from Friday on. The southwest flow should also
allow the area to warm some, which will introduce a precipitation
mix on Saturday before the precipitation comes to an end.

&&

.AVIATION /Discussion for 110300Z TAF Update/...
Issued at 1010 PM EST Sat Dec 10 2016

Minor tweaks to the current forecast including transitioning to
prevailing snowfall with MVFR visibilities at KLAF for the next
several hours.

00Z discussion follows.

VFR conditions expected through the night with deteriorating
flying conditions on Sunday as precipitation spreads over the
region.

Initial surge of moisture associated with a warm front advecting
into the region early this evening. Most of the precipitation is
not reaching the ground at this time with the boundary layer still
in the process of saturating. Should start to see some snow flakes
making it to the surface through the course of the evening with
the potential for any impacts being confined to KLAF as bulk of
the snow will focus over northern Indiana. Elsewhere...skies will
be cloudy with perhaps a few flurries. Southeast winds will be
less than 10kts.

Progressively warmer air will infiltrate the boundary layer into
Sunday afternoon as southerly flow develops. Model soundings
favoring a gradual change in precip type transitioning from south
to north with potential for a brief period of freezing rain and
sleet mixing in before rain becomes the predominant precip type by
mid to late afternoon at all sites except KLAF. At KLAF...snow
will mix with with freezing rain and sleet by late day...but not
confident surface temps can warm enough for precip to transition
to all rain prior to 00Z Sunday evening. Rain will remain the
primary precipitation type Sunday evening...with snow and sleet
mixing back in overnight Sunday as colder air returns back south
with the cold frontal passage.

Ceilings will remain VFR until midday Sunday then should gradually
fall through the afternoon to sub-IFR levels by Sunday evening.
S/SW winds will become gusty in the afternoon.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 1 AM EST Monday for INZ021-031.

&&

$$

SYNOPSIS...MK
NEAR TERM...RYAN
SHORT TERM...MK
LONG TERM....CP
AVIATION...RYAN


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